<!DOCTYPE html>
<html lang="en">

<head>
    <title>CSS</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <style>
        /* 
        同时符合如下条件:
        (1)div标签
        (2)class=a
        */
        div.a {
            color: red;
        }
    </style>
</head>

<body>
    <p class="a">
        P段落
    </p>

    <div class="a">
        DIV段落
    </div>


</body>

</html>